SuTra · Surveillance of Translation: From Molecular Mechanisms to Roles in Disease

Proteostasis is a dynamic network integrating protein biogenesis, folding, trafficking, and degradation to build a functional proteome. Disrupted proteostasis resulting the accumulation and aggregation of aberrant proteins in neurons is a hallmark of neurodegenerative diseases. This project’s overall goal is to uncover molecular mechanisms that maintain proteostasis and protect against neurodegeneration, by taking a fresh look at these processes through the lens of Ribosome-associated Quality Control (RQC), a fundamental translational surveillance mechanism whose defect causes neurodegeneration. RQC targets incomplete proteins produced by stalled ribosomes for proteolysis through two pathways mediated by factors associated with the large (60S) subunit: the E3 ubiquitin ligase, Listerin/Ltn1, and NEMF, which tags the nascent-chains with polyAla-tails that act as degrons sensed by other E3 ligases. Our preliminary data uncover that Ala-tailing modifies neurodegeneration in Ltn1-mutant mice: while Ala-tailing provides initial protection against loss of Ltn1 function, Ala-tailed proteins that evade degradation eventually accumulate and aggregate, contributing to the disease. We will create mammalian cell models, develop methods to study endogenous RQC, and use state-of-the-art biochemical and functional approaches, to: elucidate how Ala-tailed protein accumulation contributes to cellular dysfunction and toxicity (Aim 1), investigate the role of RQC in proteostasis dysfunction and cytotoxicity caused by disease-associated gene mutations (Aim 2), and uncover novel factors that sense ribosomal stalling (Aim 3). The results will lay the foundation for understanding how defects in RQC cause neuronal dysfunction, whether RQC plays a broader role in human disease, and why neurons are especially susceptible to RQC defects. These insights will provide critical molecular understanding of proteostasis and disease, which is essential for developing new target-based therapies.